The electrostatic spraying apparatus of the type having an externally air-assistive arrangement, designed for several improved parameters such as variable canopy coverage, high range target distance, applicable in transient and harsh agro-climatic conditions i.e. the presence of high wind, incorporated in the body of the sprayer, may increase the bio-efficacy.
Although, organic measures for crop protection are being preferred, chemical intervention is still the fastest and most economical way for crop protection. However, due to lack of awareness and ignorance, pesticides are being used indiscriminately leading to side effects on human health and ecosystem. Electrostatic method of pesticide application reduces off-target drift, environmental pollution and human health risks and increases the bio-efficacy and mass transfer efficiency onto the biological surfaces of crops and orchards with back deposition uniformly. So far, the equipment available in the market are uncontrolled in terms of spraying variability. Application of pesticide control, targeted pesticide delivery and variable pesticide spraying are the key to improve operation quality, reduce chemical waste, environmental pollution and low operational costs.
Electrostatic force field application to agricultural pesticide spraying is well known, it was discovered in late 1980s, references may be made to U.S. Pat. Nos. 3,630,441 and 3,698,635 A, wherein an electrostatic spraying apparatus has been developed for spraying. Although the electric charge associated with the liquid droplets was Known from the 19th century, but the actual application of electrostatic to agriculture came into existence at the end of the 19th century. A review of prior art, electrostatic process can be found in Electrostatics and its Applications, Moore, A. D., Ed., Wiley and Sons, 1973. Recently U.S. Pat. No. 7,913,938 B2 granted to Steven C. Cooper was electrostatic spray nozzle with adjustable fluid tip and interchangeable components. Numerous electrostatic nozzle patents have been granted, references may be made to U.S. Pat. Nos. 6,003,794; 6,276,617; 6,138,922 and 6,227,466, use an induction charging principle and liquid tip and air channel geometry that are similar to the above mentioned patents by Law, Cooper and Sickles. Other related work in the field of spraying may be referenced as patent numbers U.S. Pat. Nos. 5,765,761; 5,052,628; and 4,664,315, wherein the same principle has been used for the charging purposes in spraying system.
The electrostatic sprayers available and marketed so far, are being used in agriculture but the problem associated with these kind of sprayers are; directionality, variability in canopy coverage, target distance, and incapable of spraying in the presence of high wind, harsh and transient environment. Thus there is a need to provide a solution to the spray drift problem by simple mechanical means. In the existing nozzles, once the cone angle (swath width) of spraying is fixed according to the set of requirements during the design of the nozzle (diameter of the nozzle tip, flow rate etc.), the spray canopy coverage i.e. canopy covered by the spray cannot be altered further, unless the new design comes. There is not a possibility of narrowing or broadening the spray pattern during the operation of the nozzle. All nozzle tips produce a range of droplet sizes with low-drift reducing the number of small droplets. Droplets less than 100 microns are most susceptible to spray particle drift. In the case of electrostatic spraying the droplet size is in the order of less than 100 microns. The smaller droplets are more prone to drift from the target. The electrostatic repulsion among droplets is also the cause of spray drift. Presence of high wind is another cause of spray drift and presently available sprayers have no arrangement which can be used in even in normal wind. In this invention a manually controlled variable coverage high range external air-assisted electrostatic sprayer system has been developed to guide the fine droplets with the help of externally supplied high pressurized air. External air supply improves the aerodynamics conditions between spray exit from the nozzle tip and the actual target to be sprayed. The sprayer may increase the efficiency and bio-efficacy of the biological surface and reduces the air and soil pollutions.